Floor scrubbers are sometimes used on floors which are so badly soiled that one pass with the scrubber is not enough to get the floor clean, and several passes are needed to do a good job. In restricted areas the most convenient way to do this would often be to move the scrubber forward and backward over the soiled floor. However, this has not been feasible with a conventional scrubber because the suction squeegee which is mounted behind the scrub brush to suck up dirty water in normal forward moving operation is on the wrong side of the brush to work when the machine is moved backward. Dirty water would flow out in front of the brush housing and make a mess on the floor. In addition, the rear squeegee could be damaged by being dragged backward.
Scrubbing only in forward movement is not always the best way. In smaller establishments, for example fast food outlets and small retail shops, space is often so constricted that it is awkward to turn a scrubber around. Also, the scrubber can not scrub completely into the corners of a room, and they must be scrubbed manually or not at all. In such places it would often be more effective and convenient to move a scrubber back and forth, and not have to turn it around. This would simplify scrubbing in spaces such as narrow aisles and passageways. It would also make it possible to scrub completely into a corner and then back out while scrubbing in both directions, thus doing a better job than could be done with a scrubber that only works while moving in a forward direction.
Suction squeegees are commonly used on scrubbers to remove dirty water from the floor. They commonly are comprised of two flexible rubber strips or lips dragging on the floor, one ahead of the other, with the space between them connected by a flexible tube to a vacuumized tank which collects the dirty water. The tank is vacuumized by a suction blower driven by a motor and exhausting air to the atmosphere. Air is pulled under the front squeegee lip into the space between the lips, where it entrains dirty water and carries it up the tube into the tank. The water drops into the tank and the air is exhausted by the suction blower to atmosphere. Substantial power is required to run the blower, so much that it is a major concern in designing a scrubber. The system is designed to minimize air requirements, and certainly it would be intolerable to have more than one squeegee pulling air.